Conventionally, for a load cell which includes a bridge circuit formed of a strain gauge, techniques of computing an amount of change in zero based on a temperature detected by a temperature sensor, and correcting an output of the bridge circuit based on the computed amount of change in zero, have been known (for example, Japanese Patent Application Laid-Open No. 11-125555).
Also conventionally, techniques of reducing an amount of change in output of a bridge circuit, which change is caused due to change in ambient temperature by connecting a thermal sensitive resistor to an input side of the bridge circuit, to thereby compensate the sensitivity of a load cell unit (sensitivity correction), have been known (Examined Japanese Patent Application Laid-Open No. 7-069232). Further, techniques of computing an amount of change in zero based on the temperature of a load cell unit and correcting an output of a bridge circuit, by utilizing a thermal sensitive resistor for sensitivity correction as a temperature sensor, have been known (Examined Japanese Patent Application Laid-Open No. 7-069232).
Moreover, techniques of roughly compensating an output of a bridge circuit with the use of a thermal sensitive resistor which is connected in series with the bridge circuit and minutely compensating a roughly-compensated load voltage with the use of a function of temperature compensation or the like, to thereby compensate the output sensitivity of the bridge circuit, have conventionally been known (for example, Japanese Patent Application Laid-Open No. 11-064123).
It is noted that the term “zero” means a no-load output, and more specifically, a voltage (load signal) which is output from a bridge circuit of a load cell unit in a case where a voltage supplied from a power source is applied to the load cell unit when it is unloaded. It is also noted that the terms “output sensitivity” mean an amount of change in output provided from a bridge circuit in a case where a certain load is imposed on a load cell unit, that is, a value obtained by subtracting “zero” from an output of the bridge circuit.